Articles | Volume 14, issue 18
Biogeosciences, 14, 4009–4022, 2017
Biogeosciences, 14, 4009–4022, 2017

Research article 15 Sep 2017

Research article | 15 Sep 2017

Source, composition, and environmental implication of neutral carbohydrates in sediment cores of subtropical reservoirs, South China

Dandan Duan1,2, Dainan Zhang1,2, Yu Yang1, Jingfu Wang3, Jing'an Chen3, and Yong Ran1 Dandan Duan et al.
  • 1State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, Guangdong 510640, China
  • 2University of Chinese Academy of Sciences, Beijing 100049, China
  • 3State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 55002, China

Abstract. Neutral monosaccharides, algal organic matter (AOM), and carbon stable isotope ratios in three sediment cores of various trophic reservoirs in South China were determined by high-performance anion-exchange chromatography, Rock-Eval pyrolysis, and Finnigan Delta Plus XL mass spectrometry, respectively. The carbon isotopic compositions were corrected for the Suess effect. The concentrations of total neutral carbohydrates (TCHO) range from 0.51 to 6.4 mg g−1 at mesotrophic reservoirs, and from 0.83 to 2.56 mg g−1 at an oligotrophic reservoir. Monosaccharide compositions and diagnostic parameters indicate a predominant contribution of phytoplankton in each of the three cores, which is consistent with the results inferred from the corrected carbon isotopic data and C∕N ratios. The sedimentary neutral carbohydrates are likely to be structural polysaccharides and/or preserved in sediment minerals, which are resistant to degradation in the sediments. Moreover, the monosaccharide contents are highly related to the carbon isotopic data, algal productivity estimated from the hydrogen index, and increasing mean air temperature during the past 60 years. The nutrient input, however, is not a key factor affecting the primary productivity in the three reservoirs. The above evidence demonstrates that some of the resistant monosaccharides have been significantly elevated by climate change, even in low-latitude regions.

Short summary
Neutral carbohydrates, carbon isotopic composition, and algal productivity proxies in three reservoir sediment cores, South China, were investigated. Monosaccharide compositions and diagnostic parameters indicate a predominant contribution of phytoplankton in the sediment cores. Algal monosaccharide content is highly related to the algal productivity and increasing mean air temperature, but not to nutrient input, demonstrating the effect of climate warming in low-latitude regions.
Final-revised paper